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  <title>预定义常量</title>
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  <div id="layout-content"><div id="mbstring.constants" class="appendix">
 <h1>预定义常量</h1>

 <p class="simpara">下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。</p>
 <dl>
  
   <dt id="constant.mb-overload-mail">
    <strong><code>MB_OVERLOAD_MAIL</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     自 PHP 8.0.0 起已删除。
    </span>
   </dd>

  
  
   <dt id="constant.mb-overload-string">
    <strong><code>MB_OVERLOAD_STRING</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     自 PHP 8.0.0 起已删除。
    </span>
   </dd>

  
  
   <dt id="constant.mb-overload-regex">
    <strong><code>MB_OVERLOAD_REGEX</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     自 PHP 8.0.0 起已删除。
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-upper">
    <strong><code>MB_CASE_UPPER</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a full upper-case folding.
     This may change the length of the string.
     This is the mode used by mb_strtoupper().
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-lower">
    <strong><code>MB_CASE_LOWER</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a full lower-case folding.
     This may change the length of the string.
     This is the mode used by mb_strtolower().
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-title">
    <strong><code>MB_CASE_TITLE</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a full title-case conversion based on the Cased and CaseIgnorable
     derived Unicode properties.
     In particular this improves handling of quotes and apostrophes.
     This may change the length of the string.
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-fold">
    <strong><code>MB_CASE_FOLD</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a full case fold conversion which removes case distinctions
     present in the string.
     This is used for caseless matching.
     This may change the length of the string.
     Available since PHP 7.3.
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-lower-simple">
    <strong><code>MB_CASE_LOWER_SIMPLE</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a simple lower-case fold conversion.
     This does not change the length of the string.
     Available as of PHP 7.3.
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-upper-simple">
    <strong><code>MB_CASE_UPPER_SIMPLE</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs simple upper-case fold conversion.
     This does not change the length of the string.
     Available as of PHP 7.3.
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-title-simple">
    <strong><code>MB_CASE_TITLE_SIMPLE</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs simple title-case fold conversion.
     This does not change the length of the string.
     Available as of PHP 7.3.
    </span>
   </dd>

  
  
   <dt id="constant.mb-case-fold-simple">
    <strong><code>MB_CASE_FOLD_SIMPLE</code></strong> 
    (<span class="type">int</span>)
   </dt>

   <dd>

    <span class="simpara">
     Performs a simple case fold conversion which removes case distinctions
     present in the string.
     This is used for caseless matching.
     This does not change the length of the string.
     Used by case-insensitive operations internally by the MBString extension.
     Available as of PHP 7.3.
    </span>
   </dd>

  
  
   <dt id="constant.mb-oniguruma-version">
    <strong><code>MB_ONIGURUMA_VERSION</code></strong> 
    (<span class="type">string</span>)
   </dt>

   <dd>

    <span class="simpara">
     Oniguruma 版本，例如 <code class="literal">6.9.4</code>。自 PHP 7.4 起可用。
    </span>
   </dd>

  
 </dl>

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